Nearly 50 inches in 24 hours — Hawaii may have broken the national rainfall record

By John HopewellApril 27

Kelii Kinney checks on his flood-damaged property on April 15 in Anahola, Hawaii, after the Anahola River broke its banks and flooded the community downstream. (Dennis Fujimoto/Garden Island/AP)

An incredible amount of rain fell in Hawaii last week, and it was just over the course of one day. Preliminary data shows that from April 14 to 15, 49.69 inches of rain accumulated at a rain gauge in Waipa on the island of Kauai.

Kauai is one of the rainiest places on Earth, but the 24-hour inundation was far too much for the island to handle.

“From all of what I’ve seen this has been the worst flood event I’ve ever seen my 49 years here on Hanalei,” Alex Diego told the Garden Island newspaper. “The house got water in it for the first time ever.”

The National Climatic Extremes Committee will be reviewing the data and gauge site to determine the validity and potentially certify the report from Waipa, Kauai on April 14-15, 2018 as a new national 24-hour rainfall record. #hiwxpic.twitter.com/FWzI6IcCbI

To verify the accuracy of the measurement, the National Climate Extremes Committee will review the gauge site specifics and data, which is owned and operated by the Waipa Foundation and is used for watershed modeling. According to Christopher C. Burt, a weather historian at Weather Underground, the record is “plausible given the weather at the time and the region in question’s climatology” as one of the rainiest places on Earth.

The rain was caused by an upper-level low situated to the west of Kauai. The setup tapped into enhanced moisture in the lower levels of the atmosphere and created “intense anchored thunderstorms over the mountains of interior Kauai,” according to Robert Ballard, a meteorologist with the National Weather Service in Hawaii.

Ikaika Okuno rinses mud off his belongings in his garage on April 16 in Kauai. Heavy rain and flooding damaged north and south parts of the island. (Jamm Aquino/Honolulu Star-Advertiser/AP)

And what is perhaps most interesting about the potential record, said Burt, is that it was not associated with a tropical cyclone or hurricane. The current world record for 24-hour rainfall came from Tropical Storm Denise in the Indian Ocean and lashed the island of La Reunion with an almost unbelievable 71.85 inches in 1966.

Here is a list of other top 24-hour-rainfall records, all of which were related to a tropical storm or hurricane except for Waipa:

This is the same storm that we reported on several weeks ago that dumped a record 27.52 inches of rain in 24 hours on the town of Hanalei, one mile to the east of Waipa. The flash flooding and mudslides that resulted destroyed roads and bridges, cutting off locals and stranding thousands of tourists. Numerous homes across the island were destroyed or damaged, and Hawaii lawmakers have set aside $100 million for cleanup costs.